1. Field
The present disclosure relates to inorganic proton conductors and methods of preparing the same.
2. Description of the Related Art
Fuel cells are categorized according to the type of electrolyte and fuel used therein, and can be classified into polymer electrolyte membrane fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), and solid oxide fuel cells (SOFCs). In addition, the operating temperature and materials of components of fuel cells vary according to the type of electrolyte used therein.
SOFCs operate at a high temperature of between about 800 to about 1000° C., and are known to be suitable for use in decentralized power supplies. In particular, SOFCs have high electrical efficiency and can be operated using a variety of fuels, including lower purity gaseous fuels. However, due to the high temperature operation, it is expensive to maintain the durability of SOFCs in a high temperature environment, and fast on-off performance is impossible. In this sense, SOFCs are not suitable for various applications, such as for portable power supplies and for automobiles. Therefore, research on operating SOFCs at a low temperature has been actively conducted.
In PEMFCs, an electrolyte membrane is a polymer membrane that needs humidification, and thus, the conductivity of such fuel cells dramatically decreases, at a temperature of 100° C. or greater. In addition, to maintain humidified conditions, PEMFCs include a humidifier that should be carefully controlled, according to operating conditions.
As described above, as research into operating PEMFCs at high temperatures and operating SOFCs at low temperatures has been actively conducted, fuel cells capable of operating at a temperature between about 150 to about 400° C. have drawn much attention. However, electrolytes having ionic conductivity in this temperature range are not known.